Buttonhole cutting mechanism for sewing machines



" Feb 17, 1942.

A. R. WOOD BUTTONHOLE CUTTING MECHANISM FOR SEWING MACHINES Filed Jan. 24, 1940 3 Sheis-Sheet l ALFRED R. W000 Feb; 17, 1942. A. R. WOOD 2,273,242

BUI'TONHOLE CUTTING MECHANISM FOR SEWING MACHINES Filed Jan. 24, 1940 3 Sheets-Sheet 2 ALFRED R. W000 Feb. 17,1942. A. R. wooD 2,273,242

BUT'TONHOLE CUTTING MECHANISM FOR SEWING MACHINES Filed Jan. 24, 1940 s Sheets- Sheet s vn k ALF REP R. WOOD Patented Feb. 17, 1942 BUTTONHOLE CUTTING MECHANISM FOR- SEWING MACHINES Alfred R. Wood, Bridgeport, Conn., assignor to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application January 24, 1940, Serial No. 315,305

8 Claims.

This invention relates to buttonhole cutting mechanism of the reciprocatory knife and slotted work-support type represented in U. S. Patent No. 767,539; E. B. Allen; Aug. 16, 1904. Buttonhole cutting mechanism of this type is commonly applied to buttonhole sewing machines of the straight as distinguished from the eyelet-end type. A straight buttonhole machine sews a buttonhole comprising two straight side-by-side rows of zigzag lock stitches connected at their ends by groups of barring stitches extending across both rows of side stitches. After the final or finishing bar of the buttonhole is sewn there is no movement of the work-clamp to carry the work away from sewing position and the sharp knife of the buttonhole cutting mechanism is projected through the buttonhole and the knifereceiving slot in the work-supporting plate. This knife is in register with the narrow unstitched space between the adjacent rows of side stitches,

so that it will cut a slit in the material without cutting the buttonhole stitches. The length of the knife is such that the buttonhole slit cut thereby reaches as close as is practicable to the end groups of barring stitches.

In the past it has not been possible with machines of the construction disclosed in said Allen U. S. Patent No. 767,539 to cut the buttonhole slit close enough to the finishing group of barring stitches, because of interference between the needle-bar and vertically reciprocatory buttonhole cutting knife. If the knife were lengthened at its front end sufficiently to cut close to the finishing group of barring stitches it would be struck by the lower end of the needle-bar when the stitching begins.

This difiiculty is avoided in the machine of U. S. Patent No. 10,803; F. W. Ostrom; reissued Feb. 1, 1887, by turning the knife and knife-bar on a vertical axis to carry the knife sidewise of itself, when retracted, out of range of the needlebar.

Another solution of the difficulty is presented in the machine of U. S. Patent No. 1,726,922; F. A. Reece; Sept. 3, 1927, where the knife-bar is inclined to the needle-bar. With this arrangement, however, the buttonhole slit cannot be safely cut equally close to the top and bottom threads of the finishing group of barring stitches. Because of the thickness of the work, the slanting stroke of the knife carries the forward end of its cutting edge closer to the bottom threads of the finishing bar than to the top threads.

According to the present improvement, the location of the knife-holderof the machine of U. S. Patent No. 767,539 is retained but the knifecarrier is separated into two parts, the part against which the knife is seated being hung pendulum fashion from the other part or vertinally of the buttonhole, and cuts the material vertically, as closely as may be desired to the finishing group of barring stitches, without danger of loss of lateral register of the knife and I stitched buttonhole.

According to the present improvement the knife may, without danger of interference with the needle-bar, be lengthened sufiiciently to cut the buttonhole slit long enough for the needle to penetrate the out slit on the first stitch of a cut-first buttonhole, that is, a buttonhole of which the slit is out before the stitches are applied.

The present invention also affords advantages in its use in a straight buttonhole machine 'modified for tacking operations accompanied by a work-trimming operation performed by the buttonhole cutter, whereby the material trimmed alongside the tack but beyond both ends of the tack. The principle of the invention eliminates all danger of clashing between the needle-bar and knife, while retaining the desirable vertical cutting movement of the knife. The absence of lateral movement of the knife is advantageous as such movement would, in time, because of wear of the parts, disturb the necessary accuracy of register of the knife with the buttonhole slit position and result in cutting the side stitches of the buttonhole.

In the accompanying drawings:

Fig. 1 is a side elevation of a straight buttonhole sewing machine embodying the invention. Fig. 2 is a reverse side elevation of the buttonhole cutting knife supporting mechanism, the

knife being in up position. Fig. 3 is a similar view with the knife in down position. Fig. 4 is a horizontal sectional view taken substantially on the line 4-4, Fig. 2. Fig. 5 is a front view of the parts shown in Fig. 2.

The machine has the usual flat bed I from which rises the standard 2 of the overhanging bracket-arm 3 terminating in the head 4.

The stitch-forming mechanism comprises the usual endwise reciprocatory and laterally vibratory needle 5 and under-bed shuttle 6 which may be driven in the usual manner represented in U. S. Patent No. 784,291; E. B. Allen; Mar. 7, 1905.

The work-clamp is represented by the reference numeral 1 and is of conventional construction. By means of the work-clamp the work 111 is slowly moved step-by-step fashion under the endwise reciprocatory and laterally vibratory needle 5, first away from the standard 2 and then towards the standard 2, to cause the first and second rows of side zigzag stitches to be laid side by side in the work. At the ends of the rows of side stitches the usual groups 8 of barring stitches, Figs. 2 and 3, are formed.

At the completion of the buttonhole sewing operation the usual knife-bar 9 which is mounted for vertical movement in the head 4 receives sudden down and up impulses, being actuated by the usual buttonhole cutting mechanism including the levers In, H with their connecting link l2 and actuating plunger l3 of the usual stopmotion device 8, all as more fully disclosed in U. S. Patent No. 1,936,381, H. Corrall et al., Nov. 21, 1933.

Heretofore, the buttonhole cutting knife was rigidly mounted on the lower end of the knifebar 9. According to the present improvement the holder 14, in which the knife I5 is seated and to which it is clamped by the screw I5, is articulately mounted for movement on and relatively to the knife-bar, as by being horizontally pivoted at H on the cross-head l8, Fig 4, which is rigidly clamped or bolted at one end to the knife-bar 9 and is guided at its opposite end on the vertical stud-pin i9 projecting downwardly from the head 4.

The cross-head I8, Fig. 5, includes a downwardly extending fin or tongue which enters a groove 2! in the knife-holder M to prevent side play of the latter crosswise of the plane of the knife [5. The tongue 20 is normal to a plane containing the axis of the pivot IT so that the knife-holder may swing on said pivot.

The knife-holder I4 has a short rearwardly extending arm 22 which carries a laterally projecting roller stud 23 received in the cam-slot 24 in the cam-plate 25 bolted to the lower end of the head 4. The cam-slot 24 has vertically extending upper and lower end-portions connected by an inclined intermediate portion 24' which repositions the descending knife l5 just before the point thereof enters the work.

As the knife has no operative movement laterally of the 'plane thereof, there is no danger, after the wear and tear of long continued use, of loss of register between the knife and the slot IS in the work-supporting plate 26 through which the knife is projected.

The invention is not to be understood as limited to the details of construction and relative arrangement of parts shown and described. It is particularly to be understood that the invention is not limited to the specific means shown and described by which the knife-holder I4 is joined to the knife-bar 9 so as to permit the knife to be shifted relative to the knife-bar in the downstroke of the latter. Other forms of articulation equivalent to the pivot I! will readily suggest themselves to those skilled in the art. Further, the invention is not limited to the use of a stationary cam to shift the knife toward the needle position. The stationary cam 25 is, however, a simple and practical device for effecting the desired shift and control of the knife.

Having thus set forth the nature of the invention what I claim herein is:

1. In a machine of the buttonhole type, an endwise reciprocatory knife-bar, a knife-carrier, a flat knife-blade mounted on said carrier, means to swingably suspend said knife-carrier from said knife-bar, means to confine the swinging movements of the knife-carrier to planes parallel to said knife-blade, and means to impart swinging movement to the knife-carrier in the downstroke of the knife-bar.

2. In a machine of the buttonhole type, a buttonhole cutting knife, a carrier therefor, an endwise reciprocatory knife-bar on which said carrier is pivotally mounted pendulum fashion, and means to swing said carrier on its pivot in the downstroke of the knife-bar.

3. In a machine of the buttonhole type, a buttonhole cutting knife, a carrier therefor, an endwise reciprocatory knife-bar on which said carrier is pivotally mounted pendulum fashion, and a stationary cam engaged by said carrier to swing said carrier on its pivot in the downstroke of the knife-bar.

4. In a sewing machine of the buttonhole type, a bed, a work-clamp disposed to hold the work horizontally on said bed, an overhanging bracket-arm terminating at its free end in a head, a knife-bar mounted for movements endwise of itself in said head, a knife-holder pivotally hung pendulum fashion from said knife-bar, a knife mounted on the knife-holder, and a stationary cam engaged by said knife-holder to control the position at which said knife cuts the work in the downstroke of said knife-bar.

5. In a sewing machine of the buttonhole type, a work-clamp, a work-slitting knife, a knifeholder, a carrier from which said knife-holder is hung pendulum fashion to swing on a pivot transverse to the plane of said knife, said carrier being movable toward and away from the plane of the Work, and means to swing said knifeholder about its pivotal support as said knife approaches the work in its work-slitting stroke.

6. In a sewing machine of the buttonhole type, the combination with stitch-forming mechanism including a vertically endwise reciprocatory and laterally vibratory needle, of buttonhole cutting mechanism including a vertically endwise reciprocatory knife-bar, a knife hinged to said knifebar, and means to govern the motion of said knife relative to said knife-bar in the cutting stroke of the latter.

7. In a buttonhole sewing machine, a buttonhole cutter having a knife-bar, a knife-holder articulately connected to said knife-bar, a tongue and groove connection between said knife-bar and knife-holder spaced from the articulate connection between the two to prevent side play of the knife-holder, and means to shift the knifeholder relative to the knife-bar.

8. In a buttonhole sewing machine, an endwise reciprocatory knife-bar, a cross-head rigidly mounted on said knife-bar and formed with a projecting tongue, a knife-holder pivotally mounted on said cross-head and having a groove entered by said tongue, said tongue being normal to the plane containing the axis of the pivotal connection between the knife-holder and knifebar.

ALFRED R. WOOD. 

